Breakthroughs in 3D magnetic nanonetworks are expected to lead to a new generation of storage technologies

3D nanonetworks are expected to become a new era in modern solid-state physics, with many applications in photonics, biomedicine, and spintronics. The implementation of three-dimensional magnetic nanostructures can achieve ultra fast and low-energy data storage devices. Due to the competing magnetic interactions in these systems, magnetic charges or monopoles can appear, which can serve as mobile, binary information carriers.

Researchers at the University of Vienna have now designed the first three-dimensional artificial spin ice crystal lattice to carry unbound magnetic charges. The research results published in the journal NPJ Computational Materials provide theoretical evidence for the first time that in a new lattice, magnetic monopoles are stable at room temperature and can be guided as needed by an external magnetic field.

Emerging magnetic monopoles have been observed in a class of magnetic materials called spin ice. However, the atomic scale and the low temperature required for its stability limit its controllability. This has led to the development of two-dimensional artificial spin ice, where single atomic moments are replaced by magnetic nanosheets arranged on different lattices. The expansion of scale allows for the study of magnetic monopoles on more easily accessible platforms. Reverse the magnetic orientation of a specific nanoisland, causing the monopole to propagate further to a vertex, leaving a trace. This trace, known as Dirac strings, inevitably stores energy and binds monopoles, limiting their fluidity.

Researchers around Sabri Koraltan and Florian Slanovc, led by Dieter Suess at the University of Vienna, have now designed the first three-dimensional artificial spin ice lattice, combining the advantages of atoms and two-dimensional artificial spin ice.

In collaboration with the Nanomagnetism and Magnetism Group of the University of Vienna and the Theoretical Department of the Los Alamos Laboratory in the United States, the advantages of this new lattice were studied using micro electromagnetic simulations. Here, the flat two-dimensional nanosheets are replaced by magnetic rotating ellipsoids and a highly symmetric three-dimensional lattice is used. One of the first authors of the study, Sabri Koraltan, said, "Due to the degeneracy of the ground state, the tension of the Dirac string disappears, releasing the constraint on the magnetic monopole." The researchers further advanced the study to the next step, in their simulation, a magnetic monopole propagates through the lattice by applying an external magnetic field, demonstrating its application as an information carrier in three-dimensional magnetic nanonetworks.

Sabri Koraltan added, "We use the third-order and high symmetry in the new lattice to break free from magnetic monopoles and move them in the desired direction, almost like real electrons." Another first author, Florian Slanovc, summarized, "The thermal stability of monopoles at room temperature and above can lay the foundation for groundbreaking next-generation 3D storage technologies."

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